Organic light emitting display device and method for determining gamma reference voltage thereof

Abstract

An organic light emitting display device includes a display panel, a gamma reference voltage generator, and a gamma voltage generator. The gamma reference voltage generator provides the data voltage having a predetermined voltage level to the display panel, changes brightness of the display panel by sequentially reducing the data voltage, determines a critical voltage by comparing a changing amount of the brightness to a predetermined reference changing amount of the brightness, and determines the gamma reference voltage based on the critical.

What is claimed is: 
     
       1. An organic light emitting display device comprising:
 a display panel including a plurality of pixels coupled to data lines and gate lines; 
 a gamma reference voltage generator configured to determine a gamma reference voltage and to generate the gamma reference voltage; 
 a gamma voltage generator configured to generate a gamma voltage based on the gamma reference voltage; 
 a data driver configured to provide a data voltage generated based on the gamma voltage to the data lines; and 
 a scan driver configured to provide a scan signals to scan lines, 
 wherein the gamma reference voltage generator is configured to provide the data voltage to the display panel, to change a brightness of the display panel by sequentially reducing the data voltage by a fixed interval amount for each sequential reduction of the data voltage, to determine a critical voltage by comparing a changing amount of the brightness to a predetermined reference changing amount of the brightness, wherein the critical voltage is determined to be a voltage level of the data voltage below which the changing amount of the brightness is larger than the predetermined reference changing amount of the brightness, and to determine the gamma reference voltage based on the critical voltage. 
 
     
     
       2. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to determine the gamma reference voltage by adding a predetermined margin voltage to the critical voltage. 
     
     
       3. The organic light emitting display device of  claim 2 , wherein the margin voltage is determined based on a measuring environment of the brightness of the organic light emitting display device. 
     
     
       4. The organic light emitting display device of  claim 2 , wherein the margin voltage is determined based on a difference of a red driving current, a green driving current, and a blue driving current. 
     
     
       5. The organic light emitting display device of  claim 2 , wherein the margin voltage is determined according to a display brightness value (DBV) of the organic light emitting display device. 
     
     
       6. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to determine a black gamma reference voltage. 
     
     
       7. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to determine a red gamma reference voltage, a green gamma reference voltage, and a blue gamma reference voltage. 
     
     
       8. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to determine a black gamma reference voltage based on a display brightness value (DBV) of the organic light emitting display device. 
     
     
       9. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to respectively determine a red gamma reference voltage, a green gamma reference voltage, and a blue gamma reference voltage based on a display brightness value (DBV) of the organic light emitting display device. 
     
     
       10. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is configured to calculate a difference of a first brightness output from the display panel when a first data voltage is provided to the display panel and a second brightness output from the display panel when a second data voltage is provided to the display panel, and to output the difference as the changing amount of the brightness, and
 wherein a voltage level of the first data voltage is determined as the critical voltage when the difference is larger than the predetermined reference changing amount of the brightness. 
 
     
     
       11. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage is respectively determined by the organic light emitting display device. 
     
     
       12. The organic light emitting display device of  claim 1 , wherein the gamma reference voltage generator is coupled to an external brightness measuring device and is configured to receive the brightness of the display panel. 
     
     
       13. A method for determining a gamma reference voltage of an organic light emitting display device, the method comprising:
 providing a data voltage to a display panel; 
 measuring a brightness of the display panel as the data voltage is sequentially decreased by a fixed interval amount for each sequential reduction of the data voltage; 
 determining a critical voltage by comparing a changing an amount of the brightness to a predetermined reference changing amount of the brightness, wherein the critical voltage is determined to be a voltage level of the data voltage below which the changing amount of the brightness is larger than the predetermined reference changing amount of the brightness; and 
 determining the gamma reference voltage based on the critical voltage. 
 
     
     
       14. The method of  claim 13 , wherein the gamma reference voltage is determined by adding a predetermined margin voltage to the critical voltage. 
     
     
       15. The method of  claim 13 , wherein a black gamma reference voltage is determined by adding a margin voltage based on a measuring environment of brightness to the critical voltage. 
     
     
       16. The method of  claim 13 , wherein a red gamma reference voltage, a green gamma reference voltage, and a blue gamma reference voltage are respectively determined by adding a red margin voltage, a green margin voltage, and a blue margin voltage calculated by a difference between a red driving current, a green driving current, and a blue driving current to the critical voltage. 
     
     
       17. The method of  claim 13 , wherein a black gamma reference voltage is determined by adding a margin voltage calculated based on a display brightness value (DBV) of the organic light emitting display device to the critical voltage. 
     
     
       18. The method of  claim 13 , wherein a red gamma reference voltage, a green gamma reference voltage, and a blue gamma reference voltage are respectively determined by adding a margin voltage calculated based on a display brightness value (DBV) of the organic light emitting display device. 
     
     
       19. The method of  claim 13 , wherein measuring a brightness of the display panel as the data voltage is sequentially decreased includes:
 measuring a first brightness output from the display panel when a first data voltage is provided to the display panel; and 
 measuring a second brightness output from the display panel when a second data voltage that is smaller than the first data voltage is provided to the display panel. 
 
     
     
       20. The method of  claim 19 , wherein a voltage level of the first data voltage is determined as the critical voltage when a changing amount of the first brightness and the second brightness is larger than the predetermined reference changing amount of the brightness.